A VPN (Virtual Private Network) router is a device inserted between endpoint communication terminals, for adding a specific function to communication therebetween. The VPN router is a device provided between two networks for adding a function of encrypting communication therebetween.
There are two types of VPN routers. One is an IP-VPN type for connection using a VPN network provided by a carrier. The other is an Internet VPN type for connection through the internet wherein a VPN device is inserted by a user himself. In general, the former is used as a LAN-to-LAN-connecting VPN for connecting LANs to each other as shown in FIG. 9, and the latter is used as a remote access VPN for connecting a terminal PC to a LAN as shown in FIG. 10.
In FIGS. 9, 1 and 2 represent local LANs, and 3 and 4 represent VPN routers. A section between VPN routers 3, 4 is a VPN section (see patent documents 1, 2).
In FIG. 10, 5 represents a VPN terminal PC, 6 represents a VPN router, and 7 represents a local LAN. A section between VPN terminal PC 5 and VPN router 6 is an internet VPN section (see patent documents 3, 4).